Distributed State Estimation With Phasor Measurement Units (Pmu) For Power Systems

Wide-area monitoring for the power system is a key tool for preventing the power system from system wide failure. State Estimation (SE) is an essential and practical monitoring tool that has been widely used to provide estimated values for each quantity within energy management systems (EMS) in the control center. However, monitoring larger power systems coordinated by regional transmission operators has placed an enormous operational burden on current SE techniques. A distributed state estimation (DSE) algorithm with a hierarchical structure designed for the power system industry is much more computationally efficient and robust especially for monitoring a wide-area power system. Moreover, considering the deregulation of the power system industry, this method does not require sensitive data exchange between smaller areas that may be competing entities. The use of phasor measurement units (PMUs) in the SE algorithm has proven to improve the performance in terms of accuracy and converging speed. Being able to synchronize the measurements between different areas, PMUs are perfectly suited for distributed state estimation. This dissertation investigates the benefits of the DSE using PMU over a serial state estimator in wide area monitoring. A new method has been developed using available PMU data to calculate the reference angle differences between decomposed power systems in various situations, such as when the specific PMU data of the global slack bus cannot be obtained. The algorithms were tested on six bus, I standard 30 bus and I 118-bus test cases. The proposed distributed state estimator has also been implemented in a test bed to work with a power system real-time digital simulator (RTDS) that simulates the physical power system. PMUs made by SEL and GE are used to provide real-time inputs to the distributed state estimator. Simulation results demonstrated the benefits of the PMU and distributed SE techniques. Additionally a constructed test bed verified and validated the proposed algorithms and can be used for different smart grid tests

Seamless design of energy management systems

The contributions of the research are (a) an infrastructure of data acquisition systems that provides the necessary information for an automated EMS system enabling autonomous distributed state estimation, model validation, simplified protection, and seamless integration of other EMS applications, (b) an object-oriented, interoperable, and unified component model that can be seamlessly integrated with a variety of applications of the EMS, (c) a distributed dynamic state estimator (DDSE) based on the proposed data acquisition system and the object-oriented, interoperable, and unified component model, (d) a physically-based synchronous machine model, which is expressed in terms of the actual self and mutual inductances of the synchronous machine windings as a function of rotor position, for the purpose of synchronous machine parameters identification, and (e) a robust and highly efficient algorithm for the optimal power flow (OPF) problem, one of the most important applications of the EMS, based on the validated states and models of the power system provided by the proposed DDSE.Ph.D

Estimación de estado de un sistema de potencia utilizando medición fasorial sincronizada y evaluación de su implantación en el sistema de transmisión colombiano

Las PMUs se consideran como uno de los m´as importantes dispositivos de medici´on en un sistema de potencia para un futuro cercano, aunque sus beneficios han sido discutidos desde la d´ecada de los 80s en el ´ambito internacional. Su principal ventaja radica en el hecho de poder contar con mediciones fasoriales sincronizadas de tensiones y corrientes de diversos puntos del sistema de potencia, aun cuando estos se encuentren separados por grandes distancias. Obtener mediciones fasoriales sincronizadas de distintas localizaciones dentro de una red el´ectrica es posible mediante el sistema de posicionamiento global (GPS), el cual garantiza una exactitud de 1 μs para la se˜nal utilizada en el proceso de sincronizaci´on de las PMUs. Para un sistema con una frecuencia nominal de 60 Hz, se refleja en un error de ´angulo de 0,021o. Simulaciones y pruebas de campo sugieren que las PMUs pueden revolucionar la manera en que se monitorean y controlan los sistemas de potencia. Pero existen dos limitaciones importantes en la implantaci´on de esta tecnolog´ıa que son: la inversi´on que debe realizarse en un sistema de comunicaciones adecuado para soportar el tr´afico de informaci´on del sistema de medici´on fasorial sincronizado y el costo de cada unidad de medici´on, incluyendo su instalaci´on. Teniendo en cuenta estas limitaciones, el n´umero de PMUs a instalar en un sistema de potencia depende de la aplicaci´on de control o monitoreo que se desee llevar a cabo. El prop´osito de este trabajo es evaluar el impacto de implementar un sistema de medici´on fasorial sincronizado en Colombia para realizar la estimaci´on del estado del sistema, con el fin de monitorear, supervisar y controlar el sistema de potencia en tiempo real. Primero se estudian algunos de los algoritmos de localizaci´on de PMUs para implementar un sistema de medici´on fasorial sincronizado con el prop´osito de realizar la estimaci´on de estado utilizando ´unicamente mediciones fasoriales. Enseguida, se realiza una comparaci´on entre diferentes m´etodos de estimaci´on de estado que se pueden tener en cuenta cuando se tienen mediciones convencionales y fasoriales en un sistema de potencia, determinando el m´etodo de estimaci´on de estado m´as aplicable al sistema de transmisi´on colombiano. Por ´ultimo, se valora el impacto de la implementaci´on de un sistema de medici´on fasorial sincronizado en Colombia para asistir la tarea de estimaci´on de estado, evaluando sus ventajas y desventajas en comparaci´on con la forma en que se realiza esta tarea en la actualidad.Abstract. PMUs are considered one of the most important measuring devices in a power system in the near future, although its benefits have been discussed since the early 80s in the international context. Its main advantage is to have synchronized phasor measurements of voltages and currents in various parts of the power system, even though they are separated by large distances. To obtain synchronized phasor measurements from different locations within an electrical network is possible through the Global Positioning System (GPS), which guarantees an accuracy of 1 μs for the signal used in the synchronization process of PMUs. For a system with a nominal frequency of 60 Hz, it is reflected in an angle error of 0,021◦. Simulations and field tests suggest that PMUs can revolutionize the way power systems are monitored and controlled. But there are two important limitations in the implementation of this technology: the investment to be made in a communication system adequate to support the information traffic of the synchronized phasor measurement system and the cost of each measurement unit, including its installation. Given these constraints, the number of PMUs to be installed in a power system depends on the application of control or monitoring to perform. The purpose of this study is to assess the impact of implementing a synchronized phasor measurement system in Colombia to perform the state estimation of the system to monitor, supervise and control the power system in real time. First, some of optimal phasor measurement placement algorithms to implement a synchronized phasor measurement system to perform state estimation are studied. Next, a comparison is made between different state estimation methods which can take into account when conventional and phasor measurements are present in a power system, determining the state estimation method more applicable to the transmission system in Colombia. Finally, the impact of implementing this technology in Colombia is assessed, evaluating the advantages and disadvantages of a phasor measurement system compared to the manner in which this task is performed nowadays.Maestrí

Autonomous state estimation and its application to the autonomous operation of the distribution system with distributed generations

The objective of this thesis is to propose guidelines for advanced operation, control, and protection of the restructured distribution system by designing the architecture and functionality for autonomous operation of the distribution system with DGs. The proposed architecture consists of (1) autonomous state estimation and (2) applications that enable autonomous operation; in particular, three applications are discussed: setting-less component protection, instant-by-instant management, and short-term operational planning. Key elements of the proposed approach have been verified: (1) the proposed autonomous state estimation has been experimentally tested using laboratory test systems and (2) the feasibility of the setting-less component protection has been tested with numerical simulations.Ph.D